thrift: Set default validator
thrift: Set default validator

This patch sets the default validator for dynamic column families.
Doing so has no consequences in terms of behavior, but it causes the
correct type to be shown when describing the column family through
cassandra-cli.

Signed-off-by: Duarte Nunes <a60e8b7496f7715d71354fe4c06dd24017025bf1@scylladb.com>
Message-Id: <1470739773-30497-1-git-send-email-a60e8b7496f7715d71354fe4c06dd24017025bf1@scylladb.com>

avikivity/scylla,duarten/scylla,avikivity/scylla,duarten/scylla,raphaelsc/scylla,avikivity/scylla,scylladb/scylla,scylladb/scylla,raphaelsc/scylla,raphaelsc/scylla,scylladb/scylla,duarten/scylla,scylladb/scylla